The present invention relates to a light alloy bicycle rim comprising a base portion, two lateral flanks forming an outer braking surface, and a longitudinal hole provided along said lateral flanks and extending over a first portion of the height of the braking surface.
Such a bicycle rim is generally known. This known rim is formed of an extruded profile showing pinholes along the lateral flanks to join both ends of the profile by means of pins which are pressed in the pinholes. These pinholes are located at the transition between the base portion and the lateral flanks.
A drawback of the existing light alloy bicycle rims is that, due to the use of more abrasive rim brakes, the braking surfaces are subjected to considerable wear which may result after prolonged use in a destruction of the rim. More particularly, the outer peripheral portion of the lateral flanks may break off, or may bend outwards under the pressure of the tire, and may get stuck between the rim brakes. At the same time the tire will come off the rim. It is clear that this is a dangerous situation which may lead to serious accidents.
In order to avoid such accidents it has already been proposed to make an outer cut in the braking surface or to punch recesses therein. In this way, the user has an indication of the progress of the wear of the braking surfaces. However, even when the applied cut or recesses have completely disappeared, there is no real incentive to replace the rim or, in other words, there is no direct indication of the dangerous situation.
An object of the present invention is therefore to provide an original rim concept which clearly indicates when the braking surface has been worn off.
To this end, the light alloy bicycle rim according to the invention is characterized in that the first portion of the braking surface is arranged to be worn off down to the longitudinal hole so as to form a visible slit whilst a second portion of the height of the braking surface, situated radially outwards with respect to the first portion, has a thickness such that it maintains its strength when said first portion is worn off, said lateral flanks being further reinforced to prevent them from bending outwards when the braking surface is worn off down to the longitudinal hole.
In contrast to the known wear indicators set forth hereinabove, the wear of the bicycle rim according to the invention is indicated by the appearance of a visible slit in the braking surface. When such a slit is formed in the braking surface, it is immediately clear that the rim is worn off. The rim according to the present invention provides thus a clear indication that it should be replaced before any dangerous situation arises.
In practice there exists already bicycle rims having lateral flanks formed by an entirely hollow profile. When the outer wall of this hollow profile, which forms the braking surface is worn off, the strength of this profile is lost. This is especially due to the fact that the rim brake will push the braking surface inwards so that the inner wall of the hollow profile is not supported any more and will thus bend outwards under the pressure of the tire.
In a particular embodiment of the present invention, said longitudinal hole is a pinhole provided for forming a pin joint between the two extremities of the rim profile.
In this embodiment no additional longitudinal holes have to be provided along the flanks of the bicycle rim. An advantage of this embodiment is further that it provides an additional indication of the fact that the braking surfaces are worn off. Indeed, when the braking surfaces are worn off down to the pins of the pin joint, this will be felt upon braking, i.e. a shocking braking effect will be obtained.
In a preferred embodiment, a resilient element is pressed in said longitudinal hole, more particularly in the pinhole near the pin joint.
In this way said shocking braking effect will be achieved by this resilient element and will even be more pronounced than the shocking effect caused by the pins of the pin joint due to the higher frictional forces between the resilient element and the rim brake.